"Alan Holmes" wrote in message
...

I think we should be able to ask who is at the door before opening it, I
remember, and that could be a first for me, remembering that is, there
used
to be gadgets you put outside with a speaker and a microphone in, so if
someone rang the bell you could ask who it was before opening the door,
but
I have no idea where one would go for such a gadget.

So, which store do I ask at first?


I think you'd probably be better off googling for 'door entry intercom' or
something similar. Audio and video door surveillance and access control
systems have been in use in commercial premises for decades, and there are
lots of specialist firms for supply and/or fitting and maintenance, I'm sure
you'll find whatever it is you're looking for on the Net.